Technical Abstract:
Vegetative riparian buffers are popular for contaminant remediation. The process by which a contaminant is transported over, through, or beneath a riparian area and the adjacent stream discharge are hydrologic variables that will determine the effect of the stream on water quality. The quantities of runoff and baseflow that constitute the total discharge at a point in a stream are critical variables necessary to determine what portion of the stream discharge will be intercepted by the riparian buffer. Whether riparian contributions to a stream are through runoff or groundwater discharge, the impact of a riparian buffer on water quality in a stream will be proportional to the ratio of water passing through the buffer and discharge in the stream. This paper describes a method for estimating values of hydrologic determinants important in siting buffers. The method uses a 30 m digital elevation model and stream discharge data from long-term stream discharge records to define the ratio of baseflow to runoff discharge that passes through a riparian unit area. The paper includes an analysis of the potential effect of stream scale on buffer location. The analysis was tested in two stream basins in an intensively cropped area of the Midwest United States. It was found that the quality of water in small streams has a greater potential to be affected by riparian buffers than larger streams because a greater portion of their discharge is derived from riparian areas. Riparian areas along first order streams offer the greatest potential for impacting stream quality.